Computer cooling involves the removal of heat from computers and associated components, such as semiconductor devices. All semiconductor devices have some form of conduction resistance which leads to generation of heat when these devices are operated. Heat flow begins at the semiconductor junction through which electric current travels. This heat is conducted from the device body onto the package that the semiconductor is housed in, and then to the air. This heat energy increases the temperature of the semiconductor. If heat is not dissipated from the semiconductor fast enough, the semiconductor temperature may increase beyond the specified operating temperature, resulting in shorter component lifespans as well as problems such as system freezes or crashes.
A heat sink is an environment or object that absorbs heat from another object using thermal contact. Heat sinks are used to aid in the absorption of heat from the surface of a semiconductor. The goal of a heat sink is to effectively transfer heat away from the surface of the semiconductor to the surrounding air. The heat transfer can occur in three ways: conduction, convection and radiation. Conduction is the transfer of heat across matter. For example, heat is transferred from the surface of the semiconductor to the heat sink by conduction. Heat transfer through conduction can be increased by using materials with a high conduction coefficient, such as copper, silver, or gold.
Convection transfers heat energy by currents within a fluid. For example, convection occurs in the transfer of heat through currents from a heat sink to the surrounding fluid, such as air. If the currents are caused solely by a temperature gradient near the interface of the heat sink and the air, natural convection is responsible for the heat transfer. However, if the currents in the fluid are also influenced by external forces, such as current generated by a fan, then forced convection is used to transfer heat.
Radiation refers to electromagnetic radiation emitted from the surface of an object due to the object's temperature. Radiation is generated when heat from the movement of charged particles within atoms is converted into electromagnetic radiation. For example, infrared radiation is emitted by a heat sink that is heated from contact with a semiconductor. Heat transfer through a heat sink is affected by radiation because a warmer heat sink radiates more heat than a cooler heat sink.